ISLAMABAD (AP) – Tens of thousands of protesters thronged the streets of Pakistan’s capital Saturday, defying pouring rain to answer the call of a fiery cleric and a cricket star-turned-politician who are both demanding the government step down immediately.

Anti-government cleric Tahir-ul-Qadri and Pakistan’s most famous cricket player, Imran Khan, have led dual mass protests that have disrupted life across Islamabad. They demand Prime Minister Nawaz Sharif step down over alleged fraud in the country’s May 2013 election, something Sharif has refused to do.

The protesters have vowed to remain in the streets until Sharif leaves office, raising fears of political instability in the nuclear-armed nation, which only saw its first democratic transfer of power last year. While the crowds have fallen well short of the million marchers that both men promised, their presence and the government’s heightened security measures have virtually shut down business in the capital.

On Saturday, Qadri told his supporters to continue protesting until they bring about a “peaceful revolution.”

“Nawaz Sharif should be arrested when he steps down and he should not be allowed to leave the country,” he said. He also called for the dissolution of Parliament and fresh elections.

Sharif has given no indication he intends to step down, and leaders of his party said Qadri’s demands were unconstitutional.

Khan, whose camp is parallel to Qadri’s on the city’s eastern edge, also vowed Saturday to continue his protest until Sharif steps down. He called on more people to join him. “A new history is going to be recorded in Islamabad,” Khan told the protesters.

Both Khan and Qadri vowed to bring 1 million followers into the streets of Islamabad, a city of roughly 1.7 million inhabitants. But police Saturday estimated that nearly 35,000 people were present at Qadri’s rally and 25,000 at Khan’s.

The two men have maintained a separation between their rallies, although both have the same goal and both traveled to Islamabad from the eastern city of Lahore. Khan’s crowd on Saturday reflected his popularity among Pakistan’s youth, many of whom have been looking for a new political leader after decades of tight control by either the military or the country’s two longtime political parties.

Groups of young people danced to music and songs while waving political and Pakistani flags. Khan helms the Pakistan Tehreek-e-Insaf party, which is the third-largest political bloc in parliament.

Over at Qadri’s protest just meters away, the mood was more somber and organized, reflecting the cleric’s religious roots. Qadri draws his popularity from his network of mosques and religious schools across the country. Last year Qadri, who is also a Canadian national, held a protest in the capital calling for vaguely worded election reforms ahead of the country’s May poll, grinding life in Islamabad to a halt.

Shortly after Qadri’s speech, senior Cabinet minister Ahsan Iqbal urged the two opposition leaders to step back from their demands.

“We do hope that Imran Khan and Tahir-ul-Qadri will show flexibility” to end the political instability, Iqbal said.

Ahead of the protests, security forces put shipping containers on streets as roadblocks and stationed riot police around the capital.

Interior Minister Chaudhry Nisar Ali Khan said Saturday that more than 30,000 security personnel had been deployed around the two protests amid reports that suicide bombers had entered the twin cities’ area – referring to the capital and the neighboring city of Rawalpindi.

Pakistan, a nuclear-armed country of 180 million people, has largely been ruled by military dictators since it was carved out of India in 1947. The army still wields great influence in Pakistan, which is battling several militant groups, but has not taken sides in the protests. There are fears, however, that if the political unrest were to continue indefinitely or spark widespread violence it could prompt the military to intervene.

Sharif was himself overthrown in the 1999 coup that brought former army chief Pervez Musharraf to power.